Heat-transfer labels (HTLs) are commonly used in the decorating and/or labeling of commercial articles, such as, and without limitation to, containers for beverages (including alcoholic beverages, such as beer), foods, essential oils, detergents, adverse chemicals, as well as health and beauty aids. A heat-transfer label (HTL) generally includes a carrier web, a release layer of wax or non-wax coat applied to the carrier web, and an ink image printed on the release layer. The ink image is typically transferred to articles by application of heat and pressure, as described in U.S. Pat. No. 3,616,015, one of the most well known patents on heat transfer technology. UV and heat curable heat transfer labels are known in the art (e.g., see U.S. Pat. Nos. 4,231,742; 4,624,891; 5,342,725; 5,800,656; 6,042,676; 6,391,415; 6,423,406; 6,509,075; 7,014,895; 7,160,411 and U.S. Pat. Appl. Pub. No. 20120070595).
Commercially available HTL inks generally are solvent-based or water-based systems. Mandates issued by many governments to limit the volatile organic compounds (VOCs) used in industry, however, have triggered development of ultraviolet (UV) and electron beam (EB) curable inks due to their nearly 100% active components and minimal VOCs. Such systems are considered more environmentally friendly. Since the energy curable systems do not depend on evaporation of a solvent, process control can be maintained even if a coating or printing machine needs to be stopped during application. In addition, UV/EB curable inks also exhibit much better water resistance than water-based systems. Energy consumed in the drying process for UV/EB inks and coatings is lower than energy consumed in traditional oven drying of water-based or solvent-based inks and coatings. The increased speed of curing of radiation curing also reduces production time and thus increases efficiency.
Container design has evolved from generally cylindrical containers to containers that are tapered, contoured, curved or variously shaped. These contours and variation in shape of the container can lead to difficulties in application of a heat transfer label. Traditional inks and coating do not exhibit sufficient stretch, flexibility and/or extension to conform to the various shapes of some modern container designs that include more contours and unusual shapes without cracking or forming substantial defects in the heat transfer label or decoration.
Accordingly, a need exists for energy curable inks and/or coating compositions that exhibit good stretchability for use in forming flexible and extensible cured inks and coatings, such as for use in heat transfer labels. There is also a need for a sufficiently flexible and extensible heat transfer label formed from one or more curable inks and/or compositions that are adaptable for the more unusual shapes and contours of modern containers and efficient and economic methods of applying heat transfer labels.